Re: 0-600 vac to binary
- From: "Paul E. Schoen" <pstech@xxxxxxxxx>
- Date: Fri, 10 Apr 2009 02:54:06 -0400
"Ralph Barone" <invalid@xxxxxxxxxxx> wrote in message
news:invalid-CD64EE.19510209042009@xxxxxxxxxxx
In article <7hvDl.20024$%e2.7450@xxxxxxxxxxxx>,
"mook johnson" <mook@xxxxxxxx> wrote:
<TonyMatthews> wrote in message
news:hr8st41ciifh8qvkot13tbilktkahp9loj@xxxxxxxxxx
Hello
I am looking for a way to add 8 inputs to my data logger circuit. I
want to be able to detect the presence or absence of a voltage/current
from 24 vac to around 560 vac. Isoltated from the micro's port via
optoisolator. Using resistors to get 1 ma at 24 drops several watts
across the resistor at 600. Using caps I end up with large capacitors
and a lot of board space. I need only 1 ma or so to activate the
opto's ir led. So any ideas?
Tony
How about voltage divide the signals and digitize them on the hot side
of
the isolation barrior.
Then send the SPI interface signals through the digital opticouples to
the
micro.
Use an isloated powersupply for to power the A2Ds (8 channel). done
Consider adding a current source (or constant current diode) inside a
bridge rectifier in series with your optoisolator. This won't help you
for dissipation, but it will help to bring your dynamic range under
control.
Actually it might. A 1 mA current source will draw the same current at 600
VAC which will be only about 600 mW.
Also, you can use a single series diode and only draw current on the
positive excursions of the AC line, cutting power in half. The difficult
part may be getting a device that can withstand the 900 volts peak of 600
VAC.
I also like the idea of generating narrow pulses to the opto when voltage
is present.
And it should be possible to design a triac or SCR circuit to produce
perhaps 10 VDC to a 10k resistor and the opto, for all values of applied
voltage by using phase firing. That would also be rather efficient and
inexpensive.
Paul
.
- References:
- 0-600 vac to binary
- From: TonyMatthews
- Re: 0-600 vac to binary
- From: mook johnson
- Re: 0-600 vac to binary
- From: Ralph Barone
- 0-600 vac to binary
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